Saturday’s showdown was available to watch on pay-per-view in 200 countries, with viewers in the United States charged up to $99.95 to see Mayweather extend his record to 50-0 against the UFC star.

But digital security firm Irdeto claim millions of people were able to enjoy the fight on illegal streams through social media platforms such as Facebook, Youtube, Periscope and Twitch.

Though it is not uncommon for internet users to use illegal streaming sites to watch sporting events, Irdeto reported that the majority of the 200 streams they found came via social media.

With viewers in the UK having to fork out £19.95 to watch the event, a number of ‘digital Robin Hoods’ paid the fee before making it available to the world through apps such as Periscope.

Irdeto also found more than 40 online adverts advertising illegal streams for the Las Vegas showdown on a single day.

‘Live sports are a cornerstone of global piracy, with thousands of sites providing illegal content attracting millions of viewers,’ said Rory O’Connor, senior VP of cybersecurity services at Irdeto.

‘When combating live sports piracy, speed in disrupting piracy is essential… by identifying and stopping pirate streams in real-time through specialised knowledge and technology, content owners and operators are able to protect revenue and deliver a greater user experience.’

In his first fight for nearly two years, Mayweather stopped McGregor in the 10th round at the T-Mobile Arena to retire from the sport undefeated.